MODELING AND OPTIMIZATION IN ANAEROBIC BIOCONVERSION OF COMPLEX SUBSTRATES TO ACETIC AND BUTYRIC ACIDS

Cheese-processing wastewater was biologically treated to produce short -chain organic acids in laboratory scale continuously stirred tank rea ctors. A constant inoculum system was used to mimimize the experimenta l error due to the use of inconsistent inoculum. The inoculum system w as operated with dilute cheese-processing wastewater with 5000 mg solu ble chemical oxygen demand/L at pH 6.5 and 35 degrees C at 0.5 days hy draulic retention time. Response surface methodology was successfully applied to determine the optimum physiological conditions where the ma ximum rates of acetic and butyric acid production occurred. These were pH 7.01 at 36.2 degrees C and pH 7.26 at 36.2 degrees C, respectively . The lack of overall predictability for butyric acid production meant that the response surface was much more complicated than that of acet ic acid; therefore, a small change in pH or temperature could cause la rge variations in the response of butyric acid production. (C) 1997 Jo hn Wiley & Sons, Inc.